Tubing driven progressing cavity pump and method of pumping well fluid from a well

Abstract

A progressing cavity well pump system has a stator secured to a string of tubing. A drive head at the surface rotates the tubing and the stator. The pump rotor is held against rotation by an anchor mechanism. The tubing, stator, rotor and anchor mechanism are installed in the well in a single trip.

1. An apparatus for pumping a cased well, comprising:
 a wellhead assembly for location at an upper end of a cased well; 
 a string of tubing for suspension by the wellhead assembly within the well, the string of tubing having an upper portion at the wellhead assembly; 
 a drive source at the wellhead assembly and coupled to the upper portion of the string of tubing for rotating an entire length of the string of tubing; 
 a progressing cavity pump having a housing containing a stator and secured to a lower end of the string of tubing for rotation therewith, the housing having an open lower end for fluid communication with well fluid in the cased well and an open upper and in fluid communication with an interior of the string of tubing; 
 a rotor located within the stator; 
 an anchor mechanism located below the stator for gripping engagement with casing; 
 a shaft coupled to a lower end of the rotor and extending downward through the open lower end of the housing to the anchor mechanism to prevent rotation of the rotor; and 
 wherein the shaft has a smaller outer diameter than the open lower end of the housing, defining an annular intake port between the shaft and the open lower end of the housing for well fluid in the casing. 
 
   
   
     2. The apparatus according to  claim 1 , wherein the stator housing has an outer diameter larger than an inner diameter of the string of tubing. 
   
   
     3. The apparatus according to  claim 1 , wherein:
 the interior of the string of tubing has a flow area for the well fluid being pumped upward to the surface that is constant from the stator to its upper portion. 
 
   
   
     4. The apparatus according to  claim 1 , wherein the shaft comprises:
 a flexible joint extending between a lower end of the rotor and the anchor mechanism, the upper end of the flexible joint oscillating in unison with the rotor, the lower end of the flexible joint being held stationary by the anchor mechanism. 
 
   
   
     5. The apparatus according to  claim 1 , wherein the drive source comprises an electrical motor operatively engaged with the upper portion of the string of tubing. 
   
   
     6. The apparatus according to  claim 1 , further comprising:
 a manifold in engagement with the upper portion of the string of tubing above where the drive source couples to the string of tubing for receiving well fluid flowing up the string of tubing, the manifold having a closed top and an open bottom that receives an open upper end of the string of tubing, the manifold having a side outlet for discharging well fluid received from the tubing; and 
 bearings located between the manifold and the string of tubing to enable the manifold to be non rotatable while the string of tubing rotates. 
 
   
   
     7. An apparatus for pumping well fluid, comprising:
 a string of casing in a well; 
 a wellhead at an upper end of the string of casing; 
 a string of tubing suspended within the casing, the string of tubing extending through and having an upper portion extending above the wellhead; 
 a drive head above the wellhead and in engagement with the upper portion of the string of tubing for rotating an entire length of the string of tubing; 
 a progressing cavity pump having a stator secured to and extending below a lower end of the string of tubing for rotation in unison with the string of tubing, the stator having a stator housing with an outer diameter larger than an inner diameter of the string of tubing; 
 a progressing cavity pump rotor located within the stator; 
 a single flow passage extending through the progressing cavity pump, the flow passage with the interior of the of tubing for pumping well fluid up the string of tubing to the manifold; 
 an anchor mechanism in operative engagement with the rotor and gripping the casing to prevent rotation of the rotor as the stator rotates; wherein the anchor mechanism comprises:
 a mandrel carried by the rotor; and 
 a plurality of slips mounted to the mandrel for outward movement into engagement with the casing in response to axial movement of the slips relative to the mandrel; wherein
 the stator has an open lower end in fluid communication with well fluid in the casing; and 
 the mandrel has a passage therethrough with an upper port in fluid communication with well fluid in the casing above the mandrel for flowing well fluid upward into the casing and from the casing into the stator. 
 
 
 
   
   
     8. The apparatus according to  claim 7 , wherein:
 the entire length of the string of tubing has an unobstructed flow area proportional to its inner diameter. 
 
   
   
     9. The apparatus according to  claim 7  wherein rotation of the stator causes lateral oscillations of the rotor, and wherein the apparatus further comprises:
 a flexible joint extending between a lower end of the rotor and the anchor mechanism, the upper end of the flexible joint oscillating in unison with the rotor, the lower end of the rotor being held stationary by the anchor mechanism. 
 
   
   
     10. The apparatus according to  claim 7 , wherein the tubing, stator, rotor, and anchor mechanism comprise an assembly that is installed in and retrieved from the well simultaneously. 
   
   
     11. The apparatus according to  claim 7 , further comprising:
 a flex shaft housing secured to a lower end of the stator; 
 a flex shaft secured to a lower end of the rotor and extending through the flex shaft housing; 
 the upper end of the flex shaft oscillating in unison with the rotor, the lower end of the rotor being held stationary by the anchor mechanism; and 
 wherein the anchor mechanism is carried by the flex shaft and has an outer diameter larger than an internal diameter of the flex shaft housing. 
 
   
   
     12. An apparatus for pumping well fluid, comprising:
 a string of tubing for suspension within casing of a well, the string of tubing having an upper portion adapted to be located above the well; 
 a drive head in engagement with the upper portion of the string of tubing for rotating an entire length of the string of tubing; 
 a progressing cavity pump stator secured to and extending below a lower end of the string of tubing for rotation in unison with the string of tubing, the stator having a stator housing with an outer diameter larger than an inner diameter of the string of tubing; 
 a progressing cavity pump rotor located within the stator; 
 an anchor mechanism in operative engagement with the rotor for gripping the casing to prevent rotation of the rotor as the stator rotates; 
 a tubular flex joint housing secured to a lower end of the stator, the flex joint housing having an internal shoulder therein; and 
 a flex shaft extending through the flex joint housing, the flex shaft having an upper end secured to the rotor and a lower end secured to the anchor mechanism. 
 
   
   
     13. An apparatus for pumping well fluid, comprising:
 a string of tubing for suspension within casing of a well; 
 a drive head in engagement with an upper portion of the tubing for rotating the tubing; 
 a progressing cavity pump stator in operative engagement with the tubing for rotation in unison with the tubing; 
 a progressing cavity pump rotor located within the stator; 
 an anchor mechanism in operative engagement with the rotor for gripping the casing to prevent rotation of the rotor as the stator rotates; 
 a tubular flex shaft housing secured to a lower end of the stator for rotation therewith and having a reduced diameter section; 
 a flex shaft having an upper end secured to the rotor and a lower end secured to the anchor mechanism; 
 upper and lower external shoulders above and below the reduced diameter section, the external shoulders being movable in unison with the flex shaft and unable to pass through the reduced diameter section; and wherein 
 the stator is axially movable relative to the rotor between a lower position with the reduced diameter section engaging the lower external shoulder, and an upper position with the reduced diameter section engaging the upper external shoulder. 
 
   
   
     14. A method for pumping well fluid from a cased well, comprising:
 (a) inserting a rotor into a stator of a progressing cavity pump, the stator having an open lower end; 
 (b) operably coupling the stator to a string of tubing; 
 (c) lowering the string of tubing into the well and rotatably supporting an upper end of the string of tubing with a wellhead assembly at an upper end of the well, thereby defining an annulus between the stator and a casing in the well, 
 (d) coupling a drive source to the upper end of the string of tubing; 
 (e) anchoring the rotor to the casing to prevent rotation of the rotor while the stator rotates; and 
 (f) rotating with the drive source an entire length of the string of tubing and the stator and flowing well fluid from the portion of the annulus surrounding the stator into the open lower end of the stator to cause the pump to pump well fluid up the string of tubing to the surface. 
 
   
   
     15. The method according to  claim 14 , wherein step (C) further comprises:
 lowering the string of tubing, the stator and the rotor into the well simultaneously. 
 
   
   
     16. The method according to  claim 14 , wherein step (e) further comprises:
 securing an anchoring assembly to a lower end of the rotor; and 
 frictionally engaging casing in the well with the anchoring assembly to prevent rotation of the rotor while the stator rotates. 
 
   
   
     17. The method according to  claim 14  wherein step (b) comprises securing the stator to a lower end of the string of tubing such that the stator extends below the string of tubing.